U.S. patent application number 09/730388 was filed with the patent office on 2001-09-13 for electron emitting apparatus.
Invention is credited to Sasaguri, Daisuke.
Application Number | 20010020733 09/730388 |
Document ID | / |
Family ID | 26578942 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010020733 |
Kind Code |
A1 |
Sasaguri, Daisuke |
September 13, 2001 |
Electron emitting apparatus
Abstract
An electron emitting apparatus that can realize a convergence of
electron trajectories and an improved electron emission efficiency.
The apparatus comprises a substrate having a first primary surface
that is substantially planar, an electron emitting device
comprising first and second electroconductive members disposed on
the primary surface and at an interval from one another, and an
anode electrode having a substantially planar surface opposite to
the first primary surface. A voltage applying means of the
apparatus applies a potential higher than a potential applied to
the first electroconductive member to the second electroconductive
member to irradiate electrons emitted from the electron emitting
device onto the anode electrode.
Inventors: |
Sasaguri, Daisuke;
(Atsugi-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
26578942 |
Appl. No.: |
09/730388 |
Filed: |
December 6, 2000 |
Current U.S.
Class: |
257/653 ;
438/20 |
Current CPC
Class: |
H01J 1/316 20130101 |
Class at
Publication: |
257/653 ;
438/20 |
International
Class: |
H01L 021/00; H01L
029/06; H01L 031/0352 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 1999 |
JP |
11-349420 |
Nov 27, 2000 |
JP |
2000-359917 |
Claims
What is claimed is:
1. An electron emitting apparatus, comprising: (A) a substrate
having a first primary surface which is substantially plane; (B) an
electron emitting device disposed on said first primary surface,
comprising a first electroconductive member and a second
electroconductive member which are disposed at an interval; (C) an
anode electrode having a substantially plane surface opposite to
said first primary surface; (D) voltage applying means for applying
a potential higher than a potential applied to said first
electroconductive member to said second electroconductive member in
order to emit electrons from said electron emitting device; and (E)
voltage applying means for applying a potential higher than the
potential applied to said second electroconductive member in order
to irradiate the electrons emitted from said electron emitting
device onto said anode electrode; wherein a through-hole that
penetrates said second electroconductive member is defined in a
part of said second electroconductive member which exists within a
range from the gap to a distance Xs represented by the following
expression (1), an electroconductive member to which a potential
lower than said second electroconductive member is applied is
disposed under said through-hole; and Xs=H.times.Vf/(.pi..times.Va)
(1) where H is a distance between a plane of said anode electrode
and said first primary surface, Vf is a voltage applied between
said first electroconductive member and said second
electroconductive member, Va is a voltage applied between said
anode electrode and said first electroconductive member, and .pi.
is the ratio of the circumference of a circle to its diameter.
2. An electron emitting apparatus according to claim 1, wherein a
range from said gap to the distance Xs is a range on a line segment
extending from said gap toward said second electroconductive member
along the surface of said second electroconductive member by said
distance Xs.
3. An electron emitting apparatus according to claim 2, wherein the
line segment extending along the surface of said second
electroconductive member by said distance Xs is a line segment
extending from said gap toward said second electroconductive member
in a direction along which said first electroconductive member and
said second electroconductive member face each other.
4. An electron emitting apparatus according to claim 3, wherein the
line segment extending along the surface of said second
electroconductive member by said distance Xs is substantially a
straight line when said electron emitting device is viewed from
said anode electrode.
5. An electron emitting apparatus according to claim 1, wherein
said first electroconductive member and said second
electroconductive member are laminated on each other through an
insulating layer, and an electroconductive member to which a
potential lower than that of said second electroconductive member
is applied under said through-hole is said first electroconductive
member.
6. An electron emitting apparatus according to claim 5, wherein the
laminating direction of said first electroconductive member and
said second electroconductive member is substantially perpendicular
to said first primary surface.
7. An electron emitting apparatus according to claim 5, wherein
said insulating layer are made of at least two kinds of insulating
materials different in dielectric constant.
8. An electron emitting apparatus according to claim 1, wherein
said first electroconductive member and said second
electroconductive member are disposed on said first primary
surface.
9. An electron emitting apparatus according to claim 1, wherein a
plurality of said through-holes are provided.
10. An electron emitting apparatus according to claim 1, wherein
said through-hole penetrates from said second electroconductive
member to the electroconductive member to which a potential lower
than that of said second electroconductive member disposed under
said through-hole.
11. An electron emitting apparatus according to claim 1, wherein a
plurality of said electron emitting devices are disposed on said
first primary surface.
12. An electron emitting apparatus according to claim 11, wherein
said electron emitting devices are wired in a matrix.
13. An electron emitting apparatus according to claim 1, wherein an
image forming apparatus that forms an image by the electrons
emitted from said electron emitting device is disposed on said
anode electrode.
14. An electron emitting apparatus according to claim 13, wherein
said image forming member comprises a phosphor.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electron emitting
apparatus.
[0003] 2. Related Background Art
[0004] Up to now, as the electron emitting device, there have been
roughly known two kinds of electron emitting devices consisting of
a thermionic cathode and a cold cathode. The cold cathode are of
the field emission type (hereinafter referred to as "FE type"), the
metal/insulating layer/metal type (hereinafter referred to as "MIM
type"), the surface conduction type electron-emitting device, and
so on.
[0005] The examples of the FE type electron emitting devices have
been known from "Field emission" of Advance in Electron Physics,
8,89 (1956) by W. P. Dyke & W. W. Dolan, "Physical properties
of thin-film field emission cathodes with molybdenum cones" of J.
Appl. Phys., 47,5248 (1976) by C. A. Spindt, U.S. Pat. No.
5,864,147, and so on.
[0006] The examples of the MIM type electron emitting devices have
been known by "Operation of tunnel-emission devices" of J. Apply.
Phys., 32,646 (1961) by C. A. Mead, and so on.
[0007] Also, the recent examples have been introduced by
"Fluctuation-free electron emission from non-formed
metal-insulator-metal (MIM) cathodes fabricated by low current
anodic oxidation" of Jpn. J. Appl. Phys. vol. 32 (1993) pp. L1695,
by Toshiaki Kusunoki, "An MIMcathode array for cathode luminescent
displays" of IDW '96 (1996) pp. 529 by Mutsumi Suzuki, et al, and
so on.
[0008] The examples of the surface conduction type
electron-emitting devices have been disclosed in EP-A-0660357,
EP-A-0701265, "Electron trajectory analysis of surface conduction
type electron emitter displays (SEDs)" of SID 98 DIGEST, pp.
185-188 by Okuda et al, EP-A-0716439, and so on. The surface
conduction type electron-emitting devices are so designed as to
utilize a phenomenon in which electrons are emitted by allowing a
current to flow into a small-area thin film formed on a substrate
in parallel with the film surface.
[0009] The above-mentioned surface conduction type electron
emitting devices are of the planar type schematically shown in a
plan view of FIG. 18A and a cross-sectional view of FIG. 18B, and
of the vertical type schematically shown in cross-sectional views
of FIGS. 19A and 19B. In FIGS. 18A, 18B, 19A and 19B, reference
numeral 181 denotes a substrate, 182 and 184 are electrodes, 186 is
an electroconductive film, 185 is a gap and 193 is a step forming
member.
SUMMARY OF THE INVENTION
[0010] FIGS. 20 and 21 schematically show appearances in which the
devices shown in FIGS. 18A, 18B, 19A and 19B are driven,
respectively. In FIGS. 20 and 21, the same members as those in
FIGS. 18A, 18B, 19A and 19B are designed by identical
references.
[0011] In the conventional surface conduction type electron
emitting device, electrons are tunneled from the electroconductive
film 186 connected to the electrode 182 which is at a lower
potential side to the electroconductive film 186 connected to the
electrode 184 which is at a higher potential side. Then, the
electrons thus tunneled reach an anode electrode 203 after the
electrons are scattered on the higher-potential side electrode 184
and/or the higher-potential side electroconductive film 186 plural
number of times. Parts of the tunneled electrons are taken into the
higher-potential side electrode or the electroconductive film
during the above scattering process, as a result of which
sufficient electron emission efficiency cannot be ensured. In the
present specification, the electron emitting efficiency is directed
to a ratio of an emission current (Ie) that reaches the anode
electrode 203 to a device current (If) that flows between the
electrode 182 and the electrode 184 when the above device is
driven.
[0012] In order to realize the image display device, electrons
emitted from the electron emitting device are allowed to collide
with the anode electrode having a phosphor to emit a light.
However, in the image display device that requires a
higher-precision image, it is necessary that the electron
trajectories are converged, the electron emitting device is
downsized, and the electron emission efficiency is improved. In
general, as the characteristic of the electron emitting device, the
electron emission efficient and the convergence of the electron
trajectories have a relationship of trade-off, and it is difficult
to satisfy the above conditions together.
[0013] The present invention has been made to solve the above
problems, and therefore an object of the present invention is to
provide an electron emitting apparatus that can realize the
convergence of electron trajectories and an improvement of the
electron emission efficiency together.
[0014] In order to achieve the above object, according to the
present invention, there is provided an electron emitting
apparatus, comprising:
[0015] (A) a substrate having a first primary surface which is
substantially plane;
[0016] (B) an electron emitting device disposed on the first
primary surface, comprising a first electroconductive member and a
second electroconductive member which are disposed at an
interval;
[0017] (C) an anode electrode having a substantially plane surface
opposite to the first primary surface;
[0018] (D) voltage applying means for applying a potential higher
than a potential applied to the first electroconductive member to
the second electroconductive member in order to emit electrons from
the electron emitting device; and
[0019] (E) voltage applying means for applying a potential higher
than the potential applied to the second electroconductive member
in order to irradiate the electrons emitted from the electron
emitting device onto the anode electrode;
[0020] wherein a through-hole (opening) that penetrates the second
electroconductive member is defined in a part of the second
electroconductive member which exists within a range from the gap
to a distance Xs represented by the following expression (1), an
electroconductive member to which a potential lower than said
second electroconductive member is applied is disposed under said
through-hole; and
Xs=H.times.Vf/(.pi..times.Va) (1)
[0021] where H is a distance between a plane of the anode electrode
and the first primary surface, Vf is a voltage applied between the
first electroconductive member and the second electroconductive
member, Va is a voltage applied between the anode electrode and the
first electroconductive member, and .pi. is the ratio of the
circumference of a circle to its diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIGS. 1A and 1B are diagrams showing an example of an
electron emitting device according to the present invention;
[0023] FIG. 2 is a diagram showing an actual driving state of the
electron emitting device according to the present invention;
[0024] FIGS. 3A, 3B, 3C and 3D are diagrams showing an example of a
method of manufacturing the electron emitting device according to
the present invention;
[0025] FIG. 4 is a diagram showing an example of a method of
manufacturing the electron emitting device according to the present
invention;
[0026] FIG. 5 is a diagram for explanation of a potential
distribution and an electron beam in the driving state of the
electron emitting device according to the present invention;
[0027] FIG. 6 is a diagram showing an equipotential surface and the
trajectory of electrons when a width L1 of an area from which a
higher potential electrode of the electron emitting device
according to the present invention is removed is long;
[0028] FIG. 7 is a diagram showing a relationship between the
electron emission efficiency of the electron emitting device
according to the present invention and L1;
[0029] FIG. 8 is a diagram showing the electron emitting device
having two insulating layers according to the present
invention;
[0030] FIG. 9 is a diagram showing a device structure in which
steps are formed on both sides of the higher potential electrode
and a lower potential electrode;
[0031] FIG. 10 is a diagram showing an example of the electron
emitting device according to the present invention;
[0032] FIGS. 11A and 11B are diagrams showing the shape of a beam
from the electron emitting device according to the present
invention;
[0033] FIG. 12 is a diagram showing an example of a matrix wiring
in an image forming apparatus according to the present
invention;
[0034] FIG. 13 is a diagram showing an example of the image forming
apparatus according to the present invention;
[0035] FIGS. 14A and 14B are diagrams showing the structure of an
electron emitting device in accordance with a third embodiment of
the present invention;
[0036] FIGS. 15A and 15B are diagram s showing the structure of an
electron emitting device in accordance with a fourth embodiment of
the present invention;
[0037] FIGS. 16A and 16B are diagrams showing the planar type
structure of an electron emitting device in r accordance with a
seventh embodiment of the present invention;
[0038] FIGS. 17A and 17B are diagrams showing the structure of an
electron emitting device in accordance with an eighth embodiment of
the present invention;
[0039] FIGS. 18A and 18B are diagrams showing a conventional planar
type electron emitting device;
[0040] FIGS. 19A and 19B are diagrams showing a conventional
vertical type electron emitting device;
[0041] FIG. 20 is a diagram showing the field distribution and the
trajectory of electrons in the conventional planar type electron
emitting device;
[0042] FIG. 21 is a diagram showing the field distribution and the
frajectory of electrons in the conventional vertical type electron
emitting device;
[0043] FIG. 22 is a schematic diagram showing the simulation
results of electron emission from a surface conduction electron
emitting device; and
[0044] FIGS. 23A, 23B, 23C, 23D and 23E are schematic diagrams
showing a process of manufacturing the electron emitting device
according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] Now, a description will be given in more detail of preferred
embodiments of the present invention with reference to the
accompanying drawings. The dimensions, the material, the
configuration and the relative arrangement of the structural parts
described in the embodiments may be appropriately altered in
accordance with the structure and various conditions of an
apparatus to which the present invention is applied, and therefore
the scope of the present invention is not limited to the
embodiments described below.
[0046] FIGS. 1A, 1B and 2 are schematic diagrams showing an example
of a vertical type electron emitting device to which the present
invention is preferably applied, FIGS. 3A to 3D and 4 are diagrams
showing an example of a method of manufacturing the electron
emitting device shown in FIGS. 1A and 1B and an example of driving
the electron emitting device shown in FIGS. 1A and 1B. FIG. 1A is a
schematically cross-sectional view of the vertical type electron
emitting device and FIG. 1B is a schematically plan view thereof.
FIG. 2 is a schematically perspective view of an electron emitting
apparatus according to the present invention which comprises the
device shown in FIGS. 1A and 1B in which an anode electrode 8 is
disposed above the device.
[0047] In FIGS. 1A and 1B, 2 to 4, reference numeral 1 denotes a
substrate, 2 is a lower-potential side electrode, 3 is an
insulating layer, 4 is a higher-potential side electrode, 5 is a
gap, 6 is an electroconductive film, and 7 is an opening
(through-hole).
[0048] An example of a method of manufacturing the electron
emitting device in accordance with the present invention will be
described with reference to FIGS. 3A to 3D below.
[0049] (Process 1) An electrode 2 is laminated on a first primary
surface of an insulating substrate a surface of which is
satisfactorily cleaned or a substrate 1 such as a layered produce
on which SiO.sub.2 is laminated through a sputtering method or the
like.
[0050] The electrode 2 is electrically conductive and formed
through a general vacuum deposition technique such as a vapor
evaporation method or a sputtering method, a photolithography
technique or the like. The thickness of the electrode 2 is set to a
range of from several tens nm to several mm, and preferably
selected from a range of from several hundreds nm to several
.mu.m.
[0051] (Process 2) Subsequently, the insulating layer 3 is
deposited on the electrode 2. The insulating layer 3 is formed
through a general vacuum deposition method such as the sputtering
method, a thermally oxidizing method, an anodizing method or the
like. The thickness of the insulating layer 3 is set to a range of
from 3 nm to 1 .mu.m, and preferably selected from a range of from
several tens nm to several hundreds nm.
[0052] (Process 3) In addition, the electrode 4 is deposited on the
insulating layer 3. Through the above processes, a layered product
essentially consisting of the electrode 2, the insulating layer 3
and the electrode 4 is formed on the substrate 1 (FIG. 3A). The
laminating direction of the layered product is substantially
perpendicular to the first primary surface of the substrate 1. The
electrode 4 is electrically conductive as in the electrode 2 and
formed through a general vacuum deposition technique such as a
vapor evaporation method or the sputtering method, a
photolithography technique or the like.
[0053] The thickness of the electrode 4 is set to a range of from
several nm to several hundreds nm, and preferably selected from a
range of about several tens nm.
[0054] (Process 4) Subsequently, parts of the insulating layer 3
and the electrode 4 are removed through the photolithography
technique, and a step structure formed by the insulating layer 3
and the electrode 4 is defined on the electrode 2 (FIG. 3B). This
etching process may stop on the electrode 2 or may stop after a
part of the electrode 2 has been etched.
[0055] During the operation of driving the device thus structured,
the electrode 2 is set to a lower potential whereas the electrode 4
is set to a higher potential.
[0056] (Process 5) Subsequently, an area 7 (a through-hole
(opening) that penetrates the electrode 4) where a part of the
electrode 4 is removed from the substrate 1 through the
photolithography technique is formed. (FIG. 3C). In this etching
process, the process may stop on the insulating layer 3, a part of
the insulating layer 3 may be removed, or the process may stop on
the device electrode 2. As a result, the electrode 4 has the
opening portion (through-hole) 7 that penetrates in the laminating
direction of the electrode 2, the insulating layer 3 and the
electrode 4.
[0057] The area (through-hole) 7 removed in this process is formed
in the vicinity of the step formed by the electrode 4 and the
insulating layer 3. The optimum distance and configuration of the
area 7 may be appropriately selected in accordance with a size of
"a higher potential side electroconductive member" which will be
described later. The size L1 in the through-hole 7 is selected from
a range of several tens nm to several .mu.m. The details of the
size of the area 7 will be described later.
[0058] (Process 6) Then, the electroconductive film 6 is so formed
as to connect between the electrode 2 and the electrode 4 (FIG.
3C).
[0059] A length L3 of an area on which the electroconductive film 6
is deposited (refer to FIG. 1B) is appropriately set in accordance
with an electron emission length, the device structure, the
arrangement of the device and so on. However, the length L3 is
selected from a range shorter than a length L4 of an area 7 from
which the above higher-potential side electrode 4 is removed.
[0060] The electroconductive film 6 may be made of metal such as
Pd, Ru, Ag, Au, Ti, In, Cu, Cr, Fe, Zn, Sn, Ta, W or Pd, an alloy
containing two or more of those materials, oxide such as PdO,
SnO.sub.2, In.sub.2O.sub.3, PbO or Sb.sub.2O.sub.3, boride such as
HfB.sub.2, ZrB.sub.2, LaB.sub.6, CeB.sub.6, YB.sub.4, or GdB.sub.4,
carbide such as TiC, ZrC, HfC, TaC, SiC or WC, nitride such as TiN,
ZrN or HfN, semiconductor such as Si or Ge, carbon, AgMg, NiCu, Pb,
Sn or the like. Also, the resistance of the electroconductive film
6 is preferably set to a sheet resistance of 10.sup.3 to 10.sup.7
.OMEGA./square from the "forming" viewpoint which will be described
later.
[0061] (Process 7) Then, a current is allowed to flow in the
electroconductive film 6, and the gap 5 is defined in a part of the
electroconductive film 6 to form the electron emitting device (FIG.
3D). A process of forming the gap 5 by allowing the current to flow
in the electroconductive film 6 in this way is called "forming".
The electroconductive film 6 is substantially divided into two
films through the "forming" process.
[0062] In the electron emitting device according to the present
invention, there is a case in which the electroconductive film 6 is
omitted. In this case, the above gap 5 is formed by an interval
between the. electrode 2 and the electrode 4 (the thickness of the
insulating layer 3). In this case, the above process 6 and
subsequent processes can be omitted.
[0063] For that reason, in the present invention, the electrode 2
and the electroconductive film 6 connected to the electrode 2 may
be called "lower-potential side electroconductive member" together.
Similarly, in the present invention, the electrode 4 and the
electroconductive film 6 connected to the electrode 4 may be called
"higher-potential side electroconductive member" together.
[0064] In addition, in the electron emitting device according to
the present invention, there is a case in which a process 8 called
"activation" is further conducted after the gap 5 has been formed.
This process is, for example, a process of forming a carbon film on
an insulating layer 3 within the gap 5 as well as the
electroconductive film 6 in the vicinity of the gap 5 by applying a
voltage to the electrode 2 and the electrode 4 under the condition
where carbon compound exists. A narrower gap is formed in the gap 5
formed by the forming process, etc., by conducting the above
process. This activation operation may be increase the electron
emission amount.
[0065] The carbon film formed through the activation operation is
connected to "lower-potential side electroconductive member" and/or
"higher-potential side electroconductive member" with the narrower
gap (second gap) formed within the gap 5 as a boundary, which
depends on a potential applied to the electrodes 2 and 4 during the
activation operation.
[0066] For that reason, in the present invention, even if the
activation operation is conducted, there is a case in which the
carbon film connected to the "lower-potential side
electroconductive member" and the "lower-potential side
electroconductive member" are called "lower-potential side
electroconductive member" together. Similarly, in the present
invention, even if the activation operation is conducted, the
carbon film connected to the "higher-potential side
electroconductive member" and the "higher-potential side
electroconductive member" are called "higher-potential side
electroconductive member" together.
[0067] The carbon film produced in the activation operation is, for
example, a film that mainly contains graphite (which contains
so-called HOPG, PG, GC. HOPG is directed to the substantially
complete crystal structure of graphite, PG is directed to the
slightly disordered crystal structure of crystal grains about 200
.ANG., and GC is directed to the largely disordered crystal
structure of crystal grains about 20 .ANG.) and/or amorphous carbon
(which is directed to amorphous carbon and the mixture of amorphous
carbon and the microcrystal of the above graphite).
[0068] An example of a vacuum processing apparatus used in the
above "forming" process and "activation" operation will be
described with reference to FIG. 4. Also, the apparatus shown in
FIG. 4 can be used as an apparatus for measuring the
characteristics of the electron emitting device as it is. In FIG.
4, reference numeral 45 denotes a vacuum chamber, and 46 is an
exhaust pump. Reference numeral 47 denotes a supply source of
carbon compound gas used in the activation operation. The device of
the present invention is disposed within the vacuum chamber 45.
[0069] That is, reference numeral 1 denotes a substrate, 2 is a
lower-potential side electrode, 3 is an insulating layer, 4 is a
higher-potential side electrode to which a potential higher than
the electrode 2 is applied, 5 is a gap, 6 is an electroconductive
film, 41 is a power supply for applying a voltage Vf between the
electrode 2 and the electrode 4. Also, reference numeral 40 denotes
an ammeter for measuring a device current If that flows between the
lower-potential side electrode 2 and the higher-potential electrode
4, 8 is an anode electrode for complementing an emission current Ie
emitted from the device. Further, reference numeral 43 denotes a
voltage source for applying a potential higher than a potential
applied to the electrode 4 to the anode electrode 8, and 42 is an
ammeter for measuring the emission current Ie emitted from the
electron emitting device.
[0070] As an example, measurement can be made assuming that a
voltage across the anode electrode is set to a range of 0 to 10 kV,
and a distance H between the anode electrode and the electron
emitting device is set to a range of 100 .mu.m to 8 mm. In this
case, the voltage across of the anode electrode is a voltage value
between a potential applied to the lower-potential side electrode 2
and a potential applied to the anode electrode. Also, the above
distance H is indicated by a distance between the gap 5 and the
anode electrode in a narrow sense. However, since the thickness of
the layered product essentially consisting of the electrode 2, the
insulating layer 3 and the electrode 4 is very thin, the distance H
is defined as a distance between the anode electrode and the
substrate 1 without any problem.
[0071] An apparatus necessary for measuring under the vacuum
atmosphere such as a vacuum gauge not shown is disposed within the
vacuum chamber 45 so as to conduct measurement evaluation under a
desired vacuum atmosphere. The exhaust pump 46 is made up of a
normal high vacuum device system formed of a turbo pump and a
rotary pump and a super high vacuum device system formed of an ion
pump or the like.
[0072] The above activation operation can be conducted, for
example, as follows:
[0073] That is, after the substrate 1 is disposed within the vacuum
chamber 45, and a gas is exhausted from the vacuum chamber 45 into
a vacuum atmosphere, carbon compound gas is introduced into the
vacuum chamber 45 by the supply source 47 of carbon compound gas.
Then, a voltage is applied between the higher-potential side
electrode 4 and the lower-potential side electrode 2 under the
atmosphere containing carbon compound gas. It is preferable that
the voltage waveform is of a pulse waveform, and the voltage is
repeatedly applied. To achieve this manner, there are a method of
continuously applying pulses with pulse peak values as a constant
voltage, and a method of applying voltage pulses while the pulse
peak value increases.
[0074] Subsequently, the electron emission characteristic of the
electron emitting device according to the present invention as
shown in FIGS. 1A, 1B and 2 will be described in more detail.
First, the conventional surface conduction type electron emitting
device will be described. FIGS. 18A and 18B show the structure of a
conventional planar type device whereas FIGS. 19A and 19B show the
structure of a conventional vertical type device.
[0075] Now, the electron emission mechanism of the surface
conduction type electron emitting device will be described with
reference to the device shown in FIGS. 18A and 18B as an example.
The surface conduction type electron emitting device has an
electroconductive film 186 having a gap 185 of nm order, and it is
presumed that when a drive voltage Vf is applied to the
electroconductive film 186, electrons tunnel the gap, and parts of
electrons are scattered on the "higher-potential side
electroconductive member" described above as shown in FIG. 22.
[0076] Parts of electrons that have tunneled the gap 185 repeats
elastic scattering (multiple scattering) on the "higher-potential
side electroconductive member" plural number of times. Then, it is
presumed that only the electrons that exceed the following feature
distance Xs reach the anode electrode disposed above the
device.
[0077] The above feature distance Xs is represented by the
following expression (1):
Xs=(D/2){square
root}[1+{(2H.times.Vf)/(.pi..times.Va.times.D)}.sup.2].con-
gruent.(H.times.Vf)/(.pi..times.Va) (1)
[0078] where H is a distance between the electron emitting device
and the anode electrode, .pi. is the ratio of the circumference of
a circle to its diameter, D is the width of the gap 5, Vf is a
drive voltage, and Va is a voltage across the anode electrode. In
this situation, the voltage across the anode electrode is directed
to a voltage value between the potential applied to the
lower-potential side electrode 2 and the potential applied to the
anode electrode. Also, the above distance H is indicated by a
distance between the gap 5 and the anode electrode in a narrow
sense. However, since the thickness of the layered product
essentially consisting of the electrode 2, the insulating layer 3
and the electrode 4 is very thin, so the distance H can be defined
as a distance between the anode electrode and the substrate 1
without any problem.
[0079] The second approximation of the above expression (1) is
accomplished in case of Vf/d.congruent.Va/H (this is sufficiently
accomplished in case of the normal surface conduction type electron
emitting device).
[0080] For example, in the case where the drive voltage Vf is 20 V,
the anode voltage Va is 10 kV, H is 2 mm and .pi. is 3.14, the
above Xs becomes about 1 .mu.m.
[0081] The electron emission efficiency is controlled by a
reduction in the number of electrons which is partially absorbed by
the "higher-potential side electroconductive member" during the
multiple scattering process until the emitted electrons exceed the
above Xs. Although the ratio of scattered electrons (scattering
coefficient) .beta. with collision of electrons of about several
tens eV is not known, it is estimated that the ratio is about 0.1
to 0.5 per one scattering.
[0082] Because .beta. is 1 or less in the above scattering
mechanism, it is presumed that the amount of electrons extracted
into vacuum (existence probability) is reduced by exponent in
accordance with an increase in the number of times of
scattering.
[0083] Therefore, in the conventional surface conduction type
electron emitting device shown in FIGS. 18A, 18B, 19A and 19B, it
is presumed that the electrons that have tunneled the gap 185 are
scattered on the "higher-potential side electroconductive member"
within the Xs at least once, and many electrons are scattered
plural number of times. For that reason, because the electrons
taken in the "higher-potential side electroconductive member"
become the device current If, it is presumed that the electron
emission efficiency is deteriorated as the number of times of
scattering is larger.
[0084] Also, the electron beam diameter formed on the anode
electrode by the electrons emitted from the device can be described
as follows:
Lh.congruent.4 Kh.times.H{square root}(Vf/Va)
Lw.congruent.2 Kw.times.H{square root}(Vf/Va)
[0085] where Lh is a size of the beam along a longitudinal
direction of the beam, that is, a direction corresponding to a
direction perpendicular to a direction along which the
lower-potential side electrode of the surface conduction type
electron emitting device faces the higher-potential side electrode
thereof (Y-direction in FIGS. 18A, 18B, 19A and 19B). Also, Lw
shows a size of the beam along a lateral direction of the beam,
that is, a direction along which the lower-potential side electrode
of the surface conduction type electron emitting device faces the
higher-potential side electrode thereof (X-direction in FIGS. 18A,
18B, 19A and 19B). Also, Kh and Kw can approximate to about 1
although they may be slightly different depending on the device
structure.
[0086] It is understood from the above-mentioned reasons that the
electron emission efficiency can be enhanced by suppressing the
scattering of the emission electrons.
[0087] Under the above circumstances, the electron emitting device
according to the present invention can improve the electron
emission efficiency and reduce the electron beam diameter as will
be described later since the lower-potential electroconductive
member 2 is disposed under the through-hole (opening) which is
formed in a part of the "higher-potential side electroconductive
member" existing within a range of from the gap 5 to the feature
distance Xs represented by the above expression (1) and penetrates
the "higher-potential side electroconductive member", as shown in
FIGS. 1A, 1B, 16A and 16B.
[0088] In the present specification, "the higher-potential side
electroconductive member existing within a range of from the gap 5
to the feature distance Xs" means the "higher-potential side
electroconductive member" situated inside the respective spheres
when those spheres each having a radius Xs are continuously formed
in the longitudinal direction of the gap (Y-direction in FIGS. 1B
and 16B) with the gap as a center in a broad sense.
[0089] Since the width of the gap 5 (a length in the Z-direction in
FIG. 1A) is about several nm to ten several nm, it can be
substantially ignored as compared with the length of the feature
distance Xs. Also, since the electroconductive film 6 and the
higher-potential electrode 4 in the vertical type electron emitting
device shown in FIGS. 1A and 1B are very small values as compared
with the length of the feature distance Xs, there is substantially
no problem that the above feature distance is defined by the
spheres each having the radius Xs as described above.
[0090] Also, "the higher-potential side electroconductive member
existing within a range of from the gap 5 to the feature distance
Xs" is directed to the "higher-potential side electroconductive
member" within a range of from the gap 5 to a position apart from
the gap 5 by the above feature distance Xs along the surface of the
"higher-potential side electroconductive member".
[0091] Further, "a range of from the gap to the distance Xs" is
directed to a range on a line segment extending from the gap toward
the second electroconductive member along the surface of the second
electroconductive member by the above feature distance Xs.
[0092] Still further, "a line segment extending along the surface
of the second electroconductive member by the above feature
distance Xs" can be directed to a line segment extending from the
gap toward the second electroconductive member in a direction along
which the first electroconductive member and the second
electroconductive member face each other (the widthwise direction
of the gap 5).
[0093] Yet still further, "a line segment extending along the
surface of the second electroconductive member by the above feature
distance Xs" is substantially a straight line when the electron
emitting device is viewed from the anode electrode.
[0094] The electron emitting device thus structured according to
the present invention reduces the number of times of scattering of
electrons on the "higher-potential side electroconductive member"
and realizes the high efficiency by utilizing such a phenomenon
that the potential from the lower-potential side electrode 2 is
exuded onto an area (through-hole) 7 where the higher-potential
side electrode (higher-potential side electroconductive member)
does not exist as shown in FIG. 5.
[0095] Hereinafter, the feature of the electron emission according
to the present invention will be described in detail with reference
to the above-mentioned electron emitting mechanism.
[0096] First, the action of the electrons in the conventional
vertical type electron emitting device will be described with
reference to FIG. 21. After the electrons that have tunneled the
gap 185 are multiple-scattered on the surface of the
"higher-potential side electroconductive member" (a surface
perpendicular to the anode electrode plane) once or plural number
of times, parts of electrons fly out upward of the higher-potential
electrode 184. Many electrons among those electrons are again
scattered on a surface of the "higher-potential side
electroconductive member" which is substantially in parallel with
the plane of the anode electrode, and parts of the electrons reach
the anode electrode 203 above the device.
[0097] On the other hand, in case of the electron emitting device
(electron emitting apparatus) according to the present invention as
shown in FIG. 5, the potential is exuded from the lower-potential
side electrode 2 toward the area (through-hole) 7 from which a part
of the higher-potential side electrode 4 ("higher-potential side
electroconductive member") are penetratedly removed. The electrons
are influenced by that exudation so as to be suppressed from
reaching (scattering) a surface of the "higher-potential side
electroconductive member" which is substantially in parallel with
the anode electrode plane. As a result, the amount of electrons
that reach the anode electrode 8 disposed above the device
increases. For that reason, the electron emission efficiency of the
electron emitting device (electron emitting apparatus) according to
the present invention is improved as compared with the structure
shown in FIG. 21.
[0098] Further, when the position of the gap 5 is suppressed at a
position closer to the higher-potential side electrode 4 in
addition to the above structure, the number of times of electrons
on a side wall (a face substantially perpendicular to the anode
electrode plane) can be reduced.
[0099] In the present invention, since the opening area
(through-hole) 7 of the higher-potential side electrode 4
("higher-potential side electroconductive member") is disposed
within the range of from the gap 5 to the feature distance Xs, the
maximum effect is obtained so that the higher efficiency can be
made.
[0100] Also, in order to improve the electron emitting efficiency
according to the present invention, it is necessary that the
lower-potential side electrode 2 exists below the opening area 7 in
addition to the provision of the opening area (through-hole) 7 that
penetrates the higher-potential side electrode 4 ("higher-potential
side electroconductive member").
[0101] Subsequently, the optimum size of the width L1 of the area 7
in the electron emitting device according to the present invention
will be described.
[0102] In order to suppress the scattering of electrons on a face
of the "higher-potential side electroconductive member" which is
substantially in parallel with the anode electrode plane, the above
area 7 is formed. However, if L1 has a sufficient size, the
improvement effect of the electron emission characteristic is
eliminated.
[0103] In the present specification, "L1 has a sufficient size"
means the dimension of L1 by which such an electric field that the
electrons emitted from the gap 5 receive a force in a minus
direction with respect to the Z-axial direction is exuded from the
area 7 as shown in FIG. 6.
[0104] In this case, the electrons that fly out upward of the face
of the "higher-potential side electroconductive member" which is
substantially in parallel with the anode electrode plane are pushed
back by an influence of the potential formed on the area 7 and drop
down on the "higher-potential side electroconductive member", to
thereby increase the number of times of scattering. For that
reason, the electron emission efficiency starts to be
deteriorated.
[0105] FIG. 7 shows the dependency of the area (through-hole) 7 of
the electron emission efficiency on the width L1 in the
X-direction. The optimum size of L1 is determined by the minimum
dimension determined by the machining technique, the feature
distance Xs and so on, and is preferably selected from a range of
from 50 nm to 10 .mu.m.
[0106] Also, the magnitude of the potential exuded from the area 7
can be controlled by laminating at Least two kinds of layers made
of material different in dielectric constant as the insulating
layer 3. For example, as shown in FIG. 8, if an insulating layer 31
lower in dielectric constant is formed on the lower-potential
electrode 2 side and an insulating layer 32 higher in dielectric
constant is formed on the higher-potential electrode 4 side,
thereby being capable of reducing the exudation of the
potential.
[0107] The above effect can increase the exudation of the potential
in the case where the material of the higher-dielectric constant
and the material of the lower-dielectric constant are turned upside
down. Those order may be appropriately selected in accordance with
the drive voltage and the electrode size. Those effects utilize a
phenomenon that an electric field is concentrated to the material
lower in dielectric constant in the case where a voltage is applied
to the material higher in dielectric constant and the material
lower in dielectric constant and can be made by the combination of
various insulating materials different in dielectric constant.
[0108] In addition, the height of the exudation of the potential
from the area 7 can be controlled by the etching depth of the
insulating layer 3 in a process of removing the higher-potential
electrode 4 ("higher-potential side electroconductive member").
When the insulating layer 3 is removed to a certain depth, the
material lower in the dielectric constant is formed in the area.
For that reason, the exudation of the potential can be controlled
from the same effect as that in the above case where the materials
different in dielectric constant are laminated on each other.
[0109] In the electron emitting device (electron emitting
apparatus) according to the present invention, the configuration of
the area from which the higher-potential electrode
("higher-potential side electroconductive member") is removed can
be appropriately selected in accordance with the design of the
device and the device manufacturing method. For example, one or
plural circular openings may be formed, or plural slit-like
openings may be formed. The design of those configurations is
selected so as to obtain the exudation of the potential from the
lower-potential side electrode 2, and arbitrary configurations may
be selected.
[0110] Preferred drive conditions in the electron emitting device
(electron emitting apparatus) of the type shown in FIGS. 1A and 1B
according to the present invention will be described. An example
shown in FIG. 5 is the equipotential line and the electron
trajectory provided that a distance H between the electron emitting
device and the anode electrode 8 (a distance between the substrate
1 and anode electrode 8) is 2 mm, a voltage Va applied between the
anode electrode 8 and the lower-potential side electrode 2 is 10
kV, and a voltage Vf applied between the higher-potential side
electrode 4 and the lower-potential side electrode 2 is 15 V. In
the case where the electron scattering phenomenon is taken into
consideration in the electron emitting device (electron emitting
apparatus) according to the present invention, if Vf is 30 V or
less, Va and H are not particularly restricted but are selected
from an area that can retain the vacuum withstand voltage, and its
range is from one hundred V to 20 kV.
[0111] Subsequently, another structural example of the electron
emitting device according to the present invention will be
described.
[0112] The device shown in FIG. 9 is of a structure in which a
lower-potential side electrode 2, an insulating layer 3 and a
higher-potential side electrode 4 are laminated on a substrate. A
large difference from the device of the type shown in FIGS. 19A and
19B resides in the electrode structure in which the
higher-potential side electrode 4 is sandwiched between the
lower-potential side electrode 2 in its cross-sectional view (a
cross-sectional view taken along a face perpendicular to a plane of
the anode electrode) or a top view (a diagram viewed from the anode
electrode 8) (the higher-potential electrode 4 is laminated within
an area of the lower-potential electrode 2 so that the
lower-electrode 2 exists on both sides thereof.
[0113] Hereinafter, the trajectory of electrons emitted from the
device will be described.
[0114] In the above structure, the number of times of scattering of
electrons on the side wall (a surface which is substantially
perpendicular to the plane of the anode electrode) is reduced more,
the electron trajectory is curved more by a potential produced at
an opposite side of the gap 5, and the higher efficiency and the
smaller beam shape are obtained as compared with the device shown
in FIGS. 19A and 19B.
[0115] In addition, in the device thus structured, if a part of the
higher-potential side electrode 4 (higher-potential side
electroconductive member) is removed as described above, the number
of times of scattering on the "higher-potential side
electroconductive member" can be suppressed, thereby being capable
of improving the electron emission efficiency as shown in FIG.
10.
[0116] A diagram schematically comparing the beam shape of the
electron emitting device of the type shown in FIG. 5 with the beam
shape of the conventional planar type electron emitting device
shown in FIGS. 18A and 18B is shown in FIGS. 11A and 11B. In the
conventional planar type device, a majority of emitted electrons
reach the anode electrode on the upper portion of the device after
they are scattered on the "higher-potential side electroconductive
member" plural number of times.
[0117] On the other hand, in the electron emitting device (electron
emitting apparatus) according to the present invention, in addition
to the structure in which the number of times of scattering can be
suppressed, the ununiformity of the electron trajectory due to
isotropic scattering can be suppressed as much as possible, as a
result of which the beam diameter can be reduced.
[0118] The above description is given of the vertical type device
shown in FIGS. 1A and 1B and other figures to which the present
invention is applied. However, the present invention can be
preferably applied to the lateral-type electron emitting device as
shown in FIGS. 16A and 16B. In FIGS. 16A and 16B, the same parts as
those in FIGS. 1A and 1B are designated by identical references. In
the lateral-type electron emitting device shown in FIGS. 16A and
16B, an opening 7 is defined in the higher-potential side
electroconductive member (4, 6), and the potential of the
lower-potential electrode 2 under the opening 7 is exuded, thereby
being capable of suppressing the scattering on the higher-potential
side electroconductive member (4, 6).
[0119] Subsequently, a description will be given of an image
forming apparatus using the electron emitting device of the present
invention.
[0120] An image forming apparatus in which a plurality of electron
emitting devices are disposed to which the present invention can be
applied will be described with reference to FIGS. 12 and 13. In
FIG. 12, reference numeral 1011 denotes an electron source
substrate, 1012 is X-directional wirings, and 1013 is Y-directional
wirings. Reference numeral 1014 denotes electron emitting devices
according to the present invention, and 1015 is connections.
[0121] The X-directional wirings 1012 are connected with scanning
signal apply means not shown which applies a scanning signal for
selecting the rows of the electron emitting devices 1014 of the
present invention, On the other hand, the Y-directional wirings
1013 are connected with modulated signal generating means not shown
for modulating the respective columns of the electron emitting
devices 1014 of the present invention which are arranged in the
Y-direction in response to an input signal.
[0122] The drive voltage applied to the respective electron
emitting device is supplied as a difference voltage between the
scanning signal applied to the devices and the modulated signal. In
the present invention, the connections are made so that the
Y-directional wirings becomes higher in potential whereas the
X-directional wirings becomes lower in potential.
[0123] The image forming apparatus thus structured by using the
electron source arranged in the passive matrix will be described
with reference to FIG. 13. FIG. 13 is a diagram showing a display
panel of an image forming apparatus using soda lime glass as glass
material.
[0124] In FIG. 13, reference numeral 1111 denotes; an electron
source substrate in which a plurality of electron emitting devices
are arranged, 1121 is; a rear plate to which the electron source
substrate 1111 is fixed, and 1126 is a face plate where a
fluorescent film 1124, a metal back 1125 and so on are formed on an
inner surface of the glass substrate 1123.
[0125] Reference numeral 1122 denotes a support frame, and the
support frame 1122 is connected with a rear plate 1121 and the face
plate 1126 through frit glass or the like. Reference numeral 1127
denotes an envelope which is sealed by baking in vacuum at a
temperature range of 450.degree. C. for 10 minutes.
[0126] Reference numeral 1114 corresponds to the electron emitting
region in FIG. 5. Reference numeral 1112 and 1113 denote the
X-directional wirings and the Y-directional wirings which are
connected with pairs of device electrodes of the electron emitting
device of the present invention.
[0127] The envelope 1127 is made up of the face plate 1126, the
support frame 1122 and the rear plate 1121 as described above. On
the other hand, a support member not shown which is called "spacer"
is located between the face plate 1126 and the rear plate 1121, to
thereby constitute the envelope 1127 having sufficient strength
against the atmospheric pressure.
[0128] In the image forming apparatus using the electron emitting
devices according to the present invention, taking the frajectory
of emitted electrons into consideration, phosphors are aligned on
the upper portion of the device.
[0129] (Embodiments)
[0130] Hereinafter, embodiments of the present invention will be
described.
[0131] (Embodiment 1)
[0132] A device manufactured according to a first embodiment will
be described with reference to FIGS. 1A, 1B, 2 and 23A to 23E.
First, a method of manufacturing the device according to the
present invention will be described below.
[0133] (Process 1)
[0134] Ta 200 nm in thickness as a device electrode 2, SiO.sub.2 50
nm in thickness as an insulating layer 3 and Ta 50 nm in thickness
as a device electrode 4 are deposited on a quartz substrate 1 which
has been satisfactorily cleaned through the sputtering method,
respectively (FIG. 23A).
[0135] (Process 2)
[0136] Then, a mask pattern is transferred through the
photolithgraphy process. Thereafter, the higher-potential electrode
4 and the insulating layer 3 are dry-etched with a patterned resist
as a mask to form a step (FIG. 23B).
[0137] (Process 3)
[0138] Then, a part of the higher-potential electrode 4 is removed
through the photolithgraphy process to form a slit-shaped opening
area 7, and an electroconductive film 6 made of Pt-Pd 10 nm in
thickness is formed on a step portion composed of the
higher-potential side electrode 4 and the insulating layer 3 so
that the higher-potential side electrode 4 and the lower-potential
side electrode 2 are connected to each other (FIG. 23C). In this
situation, as shown in FIGS. 1A and 1B, a width L1 of the opening
area 7 is set to 0.5 .mu.m, a distance L2 from the step is set to
0.5 .mu.m and a length L4 is set to 30 .mu.m. Also, a length L3 of
the electroconductive film 6 is set to 20 .mu.m.
[0139] (Process 4) (Forming Operation)
[0140] Then, a voltage of 15 V is applied between the electrode 2
and the electrode 4 to define a gap 5 in the electroconductive thin
film 6 (FIG. 23D). In this situation, a supply voltage is a pulse
voltage and stops at a time when a resistance between the
electrodes becomes 10 M.OMEGA..
[0141] (Process 5) (Activation Operation)
[0142] Then, bipolar pulse voltages are applied between the
electrodes 2 and 4 under the atmosphere containing benzonitrile
(hereinafter referred to as "BN") of 1.3.times.10.sup.-4 Pa to form
a carbon film 10 on the inner side of the gap 5 and the
electroconductive film 6 (FIG. 23E). Through this process, a gap 5'
narrower in width is formed on the inner side of the gap 5 formed
in the above process 4. The activation operation stops at a time
when a current that flows between the electrodes 2 and 4 is
saturated.
[0143] The device manufactured in the above manner is arranged in
the vacuum chamber as shown in FIG. 4 and then driven. The drive
voltage is set to Vf=15 V and Va=10 kV, and a distance between the
electron emitting device and an anode electrode 44 (an interval
between a substrate 1 and the anode electrode 44) H is set to 2 mm.
In this example, a phosphor film is coated on the anode electrode,
and the spot size of the electron beam is observed. The electron
beam size in this example is in a range of 10% or less of the peak
luminance of the phosphor that fluoresces.
[0144] As a result, the electron beam the beam diameter of which is
converged to 100 .mu.m is obtained, and the electron emission
efficiency Ie/If represented by a ratio of the current Ie caused by
the electrons that reach the anode electrode on the upper portion
of the device to the current If that flows between the
higher-potential electrode and the lower-potential electrode of the
electron emitting device is superior to that of the device in which
no opening area 7 is provided.
[0145] The device according to this embodiment obtains the effect
of reducing the beam diameter due to the scattering suppression as
compared with the conventional device having a structure in which
the number of times of scattering is large.
[0146] (Embodiment 2)
[0147] The device is manufactured in the same shape as that in the
first embodiment. In the device according to this embodiment, an
insulating layer 3 is obtained by laminating two kinds of layers
made of SiO.sub.2 and Al.sub.2O.sub.3, respectively. The laminating
order is made so that the layer of SiO.sub.2 is formed on the upper
portion of the layer of Al.sub.2O.sub.3.
[0148] As a result, the potential that is exuded from the above
opening area can be stepped up to obtain an excellent electron
trajectory.
[0149] (Embodiment 3)
[0150] A third embodiment will be described with reference to FIGS.
14A and 14B.
[0151] In the device according to this embodiment, only a method of
shaping an opening area 7 (process 3) is different from that in the
device of the first embodiment. The process 3 conducted in this
embodiment will be described below. Other processes are conducted
in the same manner as that in the first embodiment.
[0152] (Process 3)
[0153] A circular pattern 147 which is 0.5 .mu.m in diameter is
transferred onto the higher-potential side electrode 4 at a
position apart 0.5 .mu.m from the step through the photolithography
process, and the higher-potential electrode is removed through the
dry etching.
[0154] As a result of driving the above device in the same
conditions as that in the first embodiment, the excellent electron
emission characteristic is obtained as in the first embodiment.
[0155] (Embodiment 4)
[0156] A fourth embodiment will be described with reference to
FIGS. 15A, 15B, 23A and 23B.
[0157] (Process 1)
[0158] Pt 200 nm in thickness, SiO.sub.2 50 nm in thickness and Ta
50 nm in thickness are deposited on a quartz substrate which has
been cleaned, respectively. In addition, Al 300 nm in thickness is
deposited on Ta (FIG. 23A).
[0159] (Process 2)
[0160] After Al is patterned through the photolithography process,
a resist is removed. Thereafter, a higher-potential electrode 154
and an insulating layer 153 are dry-etched with Al as a mask to
form a step (FIG. 23B).
[0161] (Process 3)
[0162] Then, aluminum used as the mask is anodized in oxalic acid
to form a plurality of opening areas in the Al film. Further, dry
etching is conducted through the opening areas of the Al film by
using the anodic aluminum oxide as a mask to form opening areas 7
shown in FIGS. 15A and 15B in a higher-potential side electrode 4.
After openings 7 are transferred, the anodic aluminum oxide used as
the mask is removed by heat phosphoric acid.
[0163] (Process 4)
[0164] An electroconductive film 6 made of Pt-Pd is formed so as to
connect the higher-potential side electrode 4 and a lower-potential
side electrode 2 as in the first embodiment, and the forming
operation and the activation operation are conducted to form a gap
5.
[0165] As a result of measuring the characteristic of the device in
this embodiment, the excellent electron emission characteristic is
obtained as in the first embodiment.
[0166] (Embodiment 5)
[0167] A fifth embodiment will be described with reference to FIG.
10.
[0168] (Process 1)
[0169] A lower-potential side electrode 2, an insulating layer 3
and a higher-potential side electrode 4 are laminated on a
substrate as in the first embodiment, and a step structure is
formed through the photolithgraphy process. In this embodiment, two
steps constructed of the higher-potential electrode 4 and the
insulating layer 3 exist, and the width of the higher-potential
side electrode is set to 4 .mu.m.
[0170] (Process 2)
[0171] Then, a part of the higher-potential side electrode 4 is
removed through the photolithgraphy process to form a slit-shaped
opening area 7 as in the first embodiment. The slit position is
designed such that L2 is set to 0.5 .mu.m and the width L1 is set
to 0.5 .mu.m.
[0172] (Process 3)
[0173] An electroconductive film 6 made of Pt-Pd is deposited in
the same manner as that in the first embodiment. In this
embodiment, Pt-Pd is selectively deposited on only one of the two
steps. Sequentially, the forming operation and the activation
operation are conducted as in the first embodiment to form a gap
5.
[0174] As a result of the above, the excellent electron emission
efficiency and electron trajectory are obtained.
[0175] (Embodiment 6)
[0176] An image forming apparatus is manufactured by using the
electron emitting devices fabricated in the first to fourth
embodiments. As an example, a case using the devices fabricated in
the first embodiment will be described.
[0177] The electron emitting devices according to the first
embodiment are disposed in a matrix of 10.times.10, and
X-directional wirings are connected to a higher-potential side
electrode, and Y-directional wirings are connected to a
lower-potential side electrode. A phosphor is disposed above the
device at a distance of 2 mm.
[0178] As a result of setting the drive conditions to Va=10 kV and
Vf=15 V, a high-precision image display can be made.
[0179] (Embodiment 7)
[0180] The device manufactured in this embodiment is described with
reference to FIGS. 16A and 16B. This embodiment ia an example in
which the present invention is applied to a planar type device.
[0181] (Process)
[0182] Al is deposited as a lower-potential side electrode 2 on a
quartz substrate through the sputtering method, and SiO.sub.2 is
deposited on the Al through the sputtering method.
[0183] (Process 2)
[0184] Then, a higher-potential side electrode 4 and the
lower-potential side electrode 2 are formed on SiO.sub.2 by a Pt
electrode. The lower-potential side electrode 2 is electrically
connected to the Al film through a contact hole defined in an
insulating layer 3.
[0185] (Process 3)
[0186] Then, a slit-shaped opening area 7 which is 1 .mu.m in width
is formed in an area apart from a gap 5 by 0.5 .mu.m.
[0187] In the planar type device manufactured through the above
method, the electron scattering on the higher-potential side
electrode 4 is suppressed, and the electron emission efficiency is
improved as compared with the conventional planar type device.
[0188] (Embodiment 8)
[0189] An eighth embodiment will be described with reference to
FIGS. 17A and 17B.
[0190] The electron emitting device is manufactured in the same
manner as that of the first embodiment. The structure manufactured
in this embodiment is such that a higher-potential side electrode 4
is perfectly separated into two electrodes (4a, 4b). These
higher-potential side electrodes 4a and 4b are connected to the
same potential through an external circuit. Similarly, in this
structure, the excellent electron emission characteristic is
obtained.
[0191] Also, this embodiment shows the structure in which the
higher-potential side electrode is perfectly separated into the two
electrodes. However, this same effect is obtained even if the
higher-potential side electrode is separated into three or more
electrodes.
[0192] As was described above, according to the present invention,
the number of times of scattering the electrons on the
higher-potential side electrode is reduced by utilizing the
exudation of the potential from the lower-potential side electrode,
thereby being capable of preventing a deterioration of the
efficiency due to the multiplex scattering and improving the
electron emission efficiency.
[0193] Also, since the number of times of scattering can be
suppressed, the ununiformity of the electron trajectory due to the
isotropic scattering can be suppressed as much as possible. Thus,
the convergence of the electron trajectory can be realized.
[0194] Further, since the improvement in the electron emission
efficiency of the electron emitting device is realized, the
electron source and the image forming apparatus which are excellent
in performance can be provided. Further, the image forming
apparatus high in precision and high in grade can be realized.
[0195] The foregoing description of the preferred embodiments of
the invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed, and modifications and
variations are possible in light of the above teachings or may be
acquired from practice of the invention. The embodiments were
chosen and described in order to explain the principles of the
invention and its practical application to enable one skilled in
the art to utilize the invention in various embodiments and with
various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the claims appended hereto, and their equivalents.
* * * * *